Blinded endorsement for blockchain

ABSTRACT

An example operation may include one or more of receiving, at an endorser node, a request message from a client system which comprises data to be stored on a blockchain, determining whether to endorse the data via invocation of chaincode which receives the data as input and executes the data against a current state of the blockchain, in response to a determination to endorse the data, generating a response message including a result of the execution and signing the response message based on a traceable blinded ring signature associated with the endorser node, and transmitting the generated response message that has been signed with the traceable blinded key ring to the client system.

TECHNICAL FIELD

This application generally relates to a blockchain endorsement process,and more particularly, to a traceable blinded ring signature which canbe used by endorser nodes to conceal an identity of the endorser nodesand the endorsement policy from being revealed.

BACKGROUND

A centralized database stores and maintains data in a single database(e.g., a database server) at one location. This location is often acentral computer, for example, a desktop central processing unit (CPU),a server CPU, or a mainframe computer. Information stored on acentralized database is typically accessible from multiple differentpoints. Multiple users or client workstations can work simultaneously onthe centralized database, for example, based on a client/serverconfiguration. A centralized database is easy to manage, maintain, andcontrol, especially for purposes of security because of its singlelocation. Within a centralized database, data redundancy is minimized asa single storing place of all data also implies that a given set of dataonly has one primary record.

However, a centralized database suffers from significant drawbacks. Forexample, a centralized database has a single point of failure.Therefore, if a hardware failure occurs, all data within the database islost and work of all users is interrupted. In addition, centralizeddatabases are highly dependent on network connectivity. As a result, theslower the connection, the amount of time needed for each databaseaccess is increased. Another drawback is the occurrence of bottleneckswhen a centralized database experiences high traffic due to a singlelocation. Furthermore, a centralized database provides limited access todata because only one copy of the data is maintained by the database. Asa result, multiple devices cannot access the same piece of data at thesame time without creating significant problems or risk overwritingstored data. Furthermore, because a database storage system has minimalto no data redundancy, data that is unexpectedly lost is very difficultto retrieve other than through manual operation from back-up storage.

Blockchain provides a solution to such drawbacks and limitationsassociated with conventional databases. Blockchain provides adistributed database in which data may only be added to the blockchainafter it is endorsed (agreed upon) by a group of untrusting partiesreferred to as endorsing nodes. To provide a level of auditability, anendorsing node stores their identity (e.g., public key) along with theirendorsement result/determination on the blockchain. Open endorsementprovides public verifiability, but can lead to potential risks such asattacks and data leakage.

For example, by mining transaction history, attackers can identifyactive endorsers or those that endorse certain type of transactions andmount targeted attacks (e.g., denial-of-service attacks, etc.) Asanother example, because submitting clients have rights to chooseendorsing peers subject to a pre-defined endorsement policy, mining alltransactions related to a specific client ID can reveal sensitiveinformation such as client's preference on endorsers, trust level ondifferent endorsers manifested through order of choice, geo-location,and the like. As such, what is needed is a solution that overcomes thesedrawbacks and limitations by completely concealing endorser nodeidentities while still enabling auditability of theendorsement/verification performed by endorsing nodes.

SUMMARY

One example embodiment provides a system that includes a processor andmemory, wherein the processor is configured to perform one or more of anetwork interface configured to receive a request message from a clientsystem which comprises data to be stored on a blockchain, and aprocessor configured to determine whether to endorse the data viainvocation of chaincode which receives the data as input and executesthe data against a current state of the blockchain, and in response to adetermination to endorse the data, generate a response message thatincludes a result of the execution and which is signed based on atraceable blinded ring signature associated with the endorser node,wherein the network interface is further configured to transmit thegenerated response message signed with the traceable blinded ringsignature to the client system

Another example embodiment provides a method that includes one or moreof receiving, at an endorser node, a request message from a clientsystem which comprises data to be stored on a blockchain, determiningwhether to endorse the data via invocation of chaincode which receivesthe data as input and executes the data against a current state of theblockchain, in response to a determination to endorse the data,generating a response message including a result of the execution andwhich is signed based on a traceable blinded ring signature associatedwith the endorser node, and transmitting the generated response messagethat has been signed with the traceable blinded key ring to the clientsystem.

A further example embodiment provides a non-transitory computer readablemedium comprising instructions, that when read by a processor, cause theprocessor to perform one or more of receiving, at an endorser node, arequest message from a client system which comprises data to be storedon a blockchain, determining whether to endorse the data via invocationof chaincode which receives the data as input and executes the dataagainst a current state of the blockchain, in response to adetermination to endorse the data, generating a response messageincluding a result of the execution and which is signed based on atraceable blinded ring signature associated with the endorser node, andtransmitting the generated response message that has been signed withthe traceable blinded key ring to the client system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating a blockchain network which implementsa traceable blinded ring for endorsement, according to exampleembodiments.

FIG. 1B is a diagram illustrating a transformation of a traceable ringsignature into a traceable blinded ring signature, according to exampleembodiments.

FIG. 2A is a diagram illustrating an example blockchain architectureconfiguration, according to example embodiments.

FIG. 2B is a diagram illustrating a blockchain transactional flow,according to example embodiments.

FIG. 3A is a diagram illustrating a permissioned network, according toexample embodiments.

FIG. 3B is a diagram illustrating another permissioned network,according to example embodiments.

FIG. 4 is a diagram illustrating a system of signing and verifying atraceable blinded ring signature, according to example embodiments.

FIG. 5 is a flow diagram illustrating a method of endorsing atransaction based on a traceable blinded ring signature, according toexample embodiments.

FIG. 6A is a diagram illustrating an example system configured toperform one or more operations described herein, according to exampleembodiments.

FIG. 6B is a diagram illustrating another example system configured toperform one or more operations described herein, according to exampleembodiments.

FIG. 6C is a diagram illustrating a further example system configured toutilize a smart contract, according to example embodiments.

FIG. 6D is a diagram illustrating yet another example system configuredto utilize a blockchain, according to example embodiments.

FIG. 7A is a diagram illustrating a process for a new block being addedto a distributed ledger, according to example embodiments.

FIG. 7B is a diagram illustrating contents of a new data block,according to example embodiments.

FIG. 7C is a diagram illustrating a blockchain for digital content,according to example embodiments.

FIG. 7D is a diagram illustrating a block which may represent thestructure of blocks in the blockchain, according to example embodiments.

FIG. 8 is a diagram illustrating an example system that supports one ormore of the example embodiments.

DETAILED DESCRIPTION

It will be readily understood that the instant components, as generallydescribed and illustrated in the figures herein, may be arranged anddesigned in a wide variety of different configurations. Thus, thefollowing detailed description of the embodiments of at least one of amethod, apparatus, non-transitory computer readable medium and system,as represented in the attached figures, is not intended to limit thescope of the application as claimed but is merely representative ofselected embodiments.

The instant features, structures, or characteristics as describedthroughout this specification may be combined or removed in any suitablemanner in one or more embodiments. For example, the usage of the phrases“example embodiments”, “some embodiments”, or other similar language,throughout this specification refers to the fact that a particularfeature, structure, or characteristic described in connection with theembodiment may be included in at least one embodiment. Thus, appearancesof the phrases “example embodiments”, “in some embodiments”, “in otherembodiments”, or other similar language, throughout this specificationdo not necessarily all refer to the same group of embodiments, and thedescribed features, structures, or characteristics may be combined orremoved in any suitable manner in one or more embodiments.

In addition, while the term “message” may have been used in thedescription of embodiments, the application may be applied to many typesof networks and data. Furthermore, while certain types of connections,messages, and signaling may be depicted in exemplary embodiments, theapplication is not limited to a certain type of connection, message, andsignaling.

Example embodiments provide methods, systems, components, non-transitorycomputer readable media, devices, and/or networks, which implementblinded endorsement for blockchain networks.

In one embodiment the application utilizes a decentralized database(such as a blockchain) that is a distributed storage system, whichincludes multiple nodes that communicate with each other. Thedecentralized database includes an append-only immutable data structureresembling a distributed ledger capable of maintaining records betweenmutually untrusted parties. The untrusted parties are referred to hereinas peers or peer nodes. Each peer maintains a copy of the databaserecords and no single peer can modify the database records without aconsensus being reached among the distributed peers. For example, thepeers may execute a consensus protocol to validate blockchain storagetransactions, group the storage transactions into blocks, and build ahash chain over the blocks. This process forms the ledger by orderingthe storage transactions, as is necessary, for consistency. In variousembodiments, a permissioned and/or a permissionless blockchain can beused. In a public or permission-less blockchain, anyone can participatewithout a specific identity. Public blockchains often involve nativecryptocurrency and use consensus based on various protocols such asProof of Work (PoW). On the other hand, a permissioned blockchaindatabase provides secure interactions among a group of entities whichshare a common goal but which do not fully trust one another, such asbusinesses that exchange funds, goods, information, and the like.

The examples herein can utilize a blockchain that operates arbitrary,programmable logic, tailored to a decentralized storage scheme andreferred to as “smart contracts” or “chaincodes.” In some cases,specialized chaincodes may exist for management functions and parameterswhich are referred to as system chaincode. The application can furtherutilize smart contracts that are trusted distributed applications whichleverage tamper-proof properties of the blockchain database and anunderlying agreement between nodes, which is referred to as anendorsement or endorsement policy. Blockchain transactions associatedwith this application can be “endorsed” before being committed to theblockchain while transactions, which are not endorsed, are disregarded.An endorsement policy allows chaincode to specify endorsers for atransaction in the form of a set of peer nodes that are necessary forendorsement. When a client sends the transaction to the peers specifiedin the endorsement policy, the transaction is executed to validate thetransaction. After validation, the transactions enter an ordering phasein which a consensus protocol is used to produce an ordered sequence ofendorsed transactions grouped into blocks.

The examples herein can utilize nodes that are the communicationentities of the blockchain system. A “node” may perform a logicalfunction in the sense that multiple nodes of different types can run onthe same physical server. Nodes are grouped in trust domains and areassociated with logical entities that control them in various ways.Nodes may include different types, such as a client or submitting-clientnode which submits a transaction-invocation to an endorser (e.g., peer),and broadcasts transaction-proposals to an ordering service (e.g.,ordering node). Another type of node is a peer node which can receiveclient submitted transactions, commit the transactions and maintain astate and a copy of the ledger of blockchain transactions. Peers canalso have the role of an endorser, although it is not a requirement. Anordering-service-node or orderer is a node running the communicationservice for all nodes, and which implements a delivery guarantee, suchas a broadcast to each of the peer nodes in the system when committingtransactions and modifying a world state of the blockchain, which isanother name for the initial blockchain transaction which normallyincludes control and setup information.

The examples herein can utilize a ledger that is a sequenced,tamper-resistant record of all state transitions of a blockchain. Statetransitions may result from chaincode invocations (i.e., transactions)submitted by participating parties (e.g., client nodes, ordering nodes,endorser nodes, peer nodes, etc.). Each participating party (such as apeer node) can maintain a copy of the ledger. A transaction may resultin a set of asset key-value pairs being committed to the ledger as oneor more operands, such as creates, updates, deletes, and the like. Theledger includes a blockchain (also referred to as a chain) which is usedto store an immutable, sequenced record in blocks. The ledger alsoincludes a state database which maintains a current state of theblockchain.

The examples herein can utilize a chain that is a transaction log whichis structured as hash-linked blocks, and each block contains a sequenceof N transactions where N is equal to or greater than one. The blockheader includes a hash of the block's transactions, as well as a hash ofthe prior block's header. In this way, all transactions on the ledgermay be sequenced and cryptographically linked together. Accordingly, itis not possible to tamper with the ledger data without breaking the hashlinks. A hash of a most recently added blockchain block represents everytransaction on the chain that has come before it, making it possible toensure that all peer nodes are in a consistent and trusted state. Thechain may be stored on a peer node file system (i.e., local, attachedstorage, cloud, etc.), efficiently supporting the append-only nature ofthe blockchain workload.

The current state of the immutable ledger represents the latest valuesfor all keys that are included in the chain transaction log. Since thecurrent state represents the latest key values known to a channel, it issometimes referred to as a world state. Chaincode invocations executetransactions against the current state data of the ledger. To make thesechaincode interactions efficient, the latest values of the keys may bestored in a state database. The state database may be simply an indexedview into the chain's transaction log, it can therefore be regeneratedfrom the chain at any time. The state database may automatically berecovered (or generated if needed) upon peer node startup, and beforetransactions are accepted.

The example embodiments are directed to a blockchain where endorsingnodes implement a traceable blinded ring. Each endorsing node isallocated a public key from a certificate authority. Meanwhile, anoperator of the blockchain may further provide each of the endorsingnodes with a respective blindness factor as well as a blinded public keyring. An endorsing node may blind its private key using the blindnessfactor, and use the blinded private key as well as the blinded publickey ring to generate a traceable blinded ring signature. The traceableblinded ring signature conceals/hides the identity of the endorsingnode, the group of endorsing nodes (the ring) as a whole, and anendorsement policy implemented by the blockchain. Accordingly, when anendorsing node signs a transaction using a traceable blinded ringsignature, the identity of the endorsing node, and the ring of endorsingnodes is concealed. Furthermore, the system provides for traceability inthat the traceable blinded ring signature can be verified to ensure theendorsement is correct, and trace to ensure that no endorsing node hassigned/endorsed the same transaction using traceable blinded ringsignature more than once.

Some benefits of the instant solutions described and depicted hereininclude anonymity, unlinkability between different transactions,unforgeability, and auditability. Anonymity is implemented because theendorser is indistinguishable from other endorsers in the endorser set.Furthermore, the identities of endorsers in the set are also hidden.Unlinkability occurs because any two signatures generated with respectto different transaction IDs (TIDs) are always unlinkable. Inparticular, it is infeasible to determine whether two transactions areendorsed by the same endorser based on the traceable blinded ringsignatures. Unforgeability occurs because every two signatures generatedby the same endorser with respect to a same transaction ID are linkable.Therefore, an endorser cannot endorse the same transaction two times.Thus, the endorsement policy can be verified accurately by countingunlinkable signatures in the endorser set.

Auditability may be performed by an auditor, a verification node, aboard, or the like. For example, to check whether an endorser endorsed acertain transaction previously, an auditor can ask the endorserbelonging to the public key ring to sign a trans-proposal with respectto a transaction ID at issue. If the new signature is linked to anendorsement signature already recorded for this trans-proposal in theledger, the auditor can determine that the endorser must have endorsedthis transaction previously.

The traceable blinded ring signature extends the notion of a traceablering signature scheme that hides an identity of the signer of a messagewithin a set of signers. However, the traceable blinded ring signatureobscures each member in the set of signers such that members of the setare not revealed in any way. According to various embodiments, ablindness factor may be added to the published public keys of theendorsers (to form a blinded ring). For example, the public key of anendorser in a ring may be multiplied by a larger integer that isinfeasible to undo. The blinding makes the endorsement policyprivacy-preserving, while traceable ring signatures simply make theactual endorsements private without compromising on public verifiabilityof the endorsements.

One of the core challenges solved by the example embodiments is makingthe process of endorsement on the blockchain platform aprivacy-preserving process, such that from the endorsement policy or theendorsement results, an adversary cannot identify the endorsers involvedin a transaction. For example, even with the endorsement results withendorser's signatures, an attacker or other entity cannot tell the trueidentity of the endorsers who actually signed (or endorsers of theblockchain). In addition, with the added blindness factor, the exampleembodiments also prevent reverse engineering of an endorsement policyfrom endorsement results. The example embodiments create a functionalimprovement (privacy-preserving endorsements) to a blockchain fabric byallowing endorsing peers to sign/endorse transactions without revealingtheir identity (public key).

Equation 1 below illustrates a traceable ring signature while Equation 2below illustrates a traceable blinded ring signature.

Ring Signature (Equation 1)

Published Public Key Set: pk_(N)={pk₁, . . . , pk_(n)}

Signing Secret Key: sk_(i)↔pk_(i)

Blinded Ring Signature (Equation 2)

Published Public Key Set: pk′_(N)={pk′₁, . . . , pk′_(n)}={pk₁g^(r) ¹ ,. . . , pk_(n)g^(r) ^(n) }

Signing Secret Key: sk′_(i)↔pk′_(i)

The blinding factor g^(r) ^(i) shown in Equation 2, prevents the blindedpublic key ring from being traced back to a set of endorser nodes.

FIG. 1A illustrates a blockchain network 100 which implements atraceable blinded ring signature for endorsement, according to exampleembodiments. Referring to FIG. 1A, the blockchain network 100 implementsa blockchain (not shown) which may be replicated and distributed among aplurality of peer nodes 120-125. In the example of FIG. 1A, each of thepeer nodes 120-125 may store a copy of the blockchain. However, peernodes 123, 124, and 125, perform roles of endorsers while peer nodes120, 121, and 122 do not perform the role of endorsement. A clientsystem 130 may communicate with any of the peer nodes 120-125 as agateway to access (store, retrieve, modify, etc.) data on theblockchain. For example, the client system 130 may transmit atransaction request to peer node 121. The transaction type is notlimited to any particular type.

In this example, an endorsement policy may dictate that at least two ofendorser nodes 123, 124, and 125 endorse a transaction before it can bestored on the blockchain. Therefore, before the transaction submitted bythe client 130 can be stored throughout the blockchain, it must receiveendorsements from any two of the endorser nodes 123, 124, and 125. Eachendorser node may simulate the transaction against a current state ofthe blockchain database to ensure that the transaction is valid. Anexample of the endorsement process is described with respect to FIG. 2B.After determining whether to endorse the transaction, each of theendorser nodes 123, 124, and 125 generate a response message andtransmit the response message to the client node (peer node 121 andclient 130). According to various embodiments, rather than sign theresponse message with a traditional public key, each endorser node maysign the response message with its own blinded private key and theblinded public key ring, which results in a traceable blinded ringsignature. In this case, endorser nodes 123, 124, and 125 hold traceableblind ring signatures A, B, and C, respectively.

Therefore, nodes that have access to the blockchain are not able toidentify any of the endorser nodes 123, 124, and 125. That is, theidentity of the endorser nodes 123, 124, and 125 is obscured. Therefore,another party accessing the blockchain cannot determine who the endorsernodes 123-125 are. Furthermore, the traceable blinded ring signaturealso prevents discovery of an endorsement policy (i.e., two out of anythree of endorser nodes).

The example embodiments hide both the identity of an endorser in theendorsement results, and the actual endorsement policy. This is acritical step towards achieving transaction privacy in permissionedblockchain networks such as Hyperledger Fabric. Apart from ensuringprivacy, it can also help in preventing targeted security attacks (e.g.,denial of service attacks) in the blockchain network.

FIG. 1B illustrates a process 150 of transforming of a traceable ringsignature (public key) into a traceable blinded ring signature (secretkey) an endorsing peer obtaining a blinded secret key and blinded publickey ring required for generating the traceable blinded ring signature,according to example embodiments. The process 150 may be performed byany of the endorsing nodes. In a first step 152, the endorsing nodereceives a public key certificate which may be provided from acertificate authority (CA). The identity of an endorser is an endorser'spublic key, issued in the form of a certificate. The certificate isissued by the certificate authority and states that this public key is avalid public key for a particular peer. The certificate contains thepeer's organization ID and other information.

In a second step 154, the endorsing peer receives a blindness factor aswell as a blinded public key ring from a board or otheroperator/controller of the blockchain. The blindness factor may includea larger random integer. In a third step 156, the endorsing peer createsthe blinded public/private key. For example, the blindness factor may beadded to the public/private key through multiplication of a factor(large random integer) to the original public/private key. An endorser'sidentity is the endorser's public key which is known by all participantsin the network. Therefore, by adding a blindness factor to the publickey to generate the blinded public key, the system disguises theidentities of the endorsers. The public key is typically used to verifythe signature of the endorser in the original design of Fabric. However,in the example embodiments, the signature is generated using the newblinded private key and blinded public key ring. As a result, theoriginal public key cannot be used for verification and hence privacy isprotected.

FIG. 2A illustrates a blockchain architecture configuration 200,according to example embodiments. Referring to FIG. 2A, the blockchainarchitecture 200 may include certain blockchain elements, for example, agroup of blockchain nodes 202. The blockchain nodes 202 may include oneor more nodes 204-210 (these four nodes are depicted by example only).These nodes participate in a number of activities, such as blockchaintransaction addition and validation process (consensus). One or more ofthe blockchain nodes 204-210 may endorse transactions based onendorsement policy and may provide an ordering service for allblockchain nodes in the architecture 200. A blockchain node may initiatea blockchain authentication and seek to write to a blockchain immutableledger stored in blockchain layer 216, a copy of which may also bestored on the underpinning physical infrastructure 214. The blockchainconfiguration may include one or more applications 224 which are linkedto application programming interfaces (APIs) 222 to access and executestored program/application code 220 (e.g., chaincode, smart contracts,etc.) which can be created according to a customized configurationsought by participants and can maintain their own state, control theirown assets, and receive external information. This can be deployed as atransaction and installed, via appending to the distributed ledger, onall blockchain nodes 204-210.

The blockchain base or platform 212 may include various layers ofblockchain data, services (e.g., cryptographic trust services, virtualexecution environment, etc.), and underpinning physical computerinfrastructure that may be used to receive and store new transactionsand provide access to auditors which are seeking to access data entries.The blockchain layer 216 may expose an interface that provides access tothe virtual execution environment necessary to process the program codeand engage the physical infrastructure 214. Cryptographic trust services218 may be used to verify transactions such as asset exchangetransactions and keep information private.

The blockchain architecture configuration of FIG. 2A may process andexecute program/application code 220 via one or more interfaces exposed,and services provided, by blockchain platform 212. The code 220 maycontrol blockchain assets. For example, the code 220 can store andtransfer data, and may be executed by nodes 204-210 in the form of asmart contract and associated chaincode with conditions or other codeelements subject to its execution. As a non-limiting example, smartcontracts may be created to execute reminders, updates, and/or othernotifications subject to the changes, updates, etc. The smart contractscan themselves be used to identify rules associated with authorizationand access requirements and usage of the ledger. For example, theinformation 226 may include data to be processed by one or moreprocessing entities (e.g., virtual machines) included in the blockchainlayer 216. The result 228 may include processing results of executingthe chaincode. The physical infrastructure 214 may be utilized toretrieve any of the data or information described herein.

A smart contract may be created via a high-level application andprogramming language, and then written to a block in the blockchain. Thesmart contract may include executable code which is registered, stored,and/or replicated with a blockchain (e.g., distributed network ofblockchain peers). A transaction is an execution of the smart contractcode which can be performed in response to conditions associated withthe smart contract being satisfied. The executing of the smart contractmay trigger a trusted modification(s) to a state of a digital blockchainledger. The modification(s) to the blockchain ledger caused by the smartcontract execution may be automatically replicated throughout thedistributed network of blockchain peers through one or more consensusprotocols.

The smart contract may write data to the blockchain in the format ofkey-value pairs. Furthermore, the smart contract code can read thevalues stored in a blockchain and use them in application operations.The smart contract code can write the output of various logic operationsinto the blockchain. The code may be used to create a temporary datastructure in a virtual machine or other computing platform. Data writtento the blockchain can be public and/or can be encrypted and maintainedas private. The temporary data that is used/generated by the smartcontract is held in memory by the supplied execution environment, thendeleted once the data needed for the blockchain is identified.

A chaincode may include the code interpretation of a smart contract,with additional features. As described herein, the chaincode may beprogram code deployed on a computing network, where it is executed andvalidated by chain validators together during a consensus process. Thechaincode receives a hash and retrieves from the blockchain a hashassociated with the data template created by use of a previously storedfeature extractor. If the hashes of the hash identifier and the hashcreated from the stored identifier template data match, then thechaincode sends an authorization key to the requested service. Thechaincode may write to the blockchain data associated with thecryptographic details.

FIG. 2B illustrates an example of a blockchain transactional flow 250between nodes of the blockchain in accordance with an exampleembodiment. Referring to FIG. 2B, the transaction flow may include atransaction proposal 291 sent by an application client node 260 to anendorsing peer node 281. The endorsing peer 281 may verify the clientsignature and execute a chaincode function to initiate the transaction.The output may include the chaincode results, a set of key/valueversions that were read in the chaincode (read set), and the set ofkeys/values that were written in chaincode (write set). The proposalresponse 292 is sent back to the client 260 along with an endorsementsignature, if approved. According to various embodiments, instead ofsigning the proposal response 292 with a public key, the endorsing peer281 may sign the proposal response 292 with the blinded private key andblinded public key ring, which results in a traceable blinded ringsignature. The traceable blind ring signature may be unique to theendorsing peer 281 in an example in which the system includes multipleendorsing peers. That is, each endorsing peer may include their ownunique traceable blind ring signature.

The client 260 assembles the endorsements into a transaction payload 293and broadcasts it to an ordering service node 284. The ordering servicenode 284 then delivers ordered transactions as blocks to all peers281-283 on a channel. Before committal to the blockchain, each peer281-283 may validate the transaction. For example, the peers may checkthe endorsement policy to ensure that the correct allotment of thespecified peers have signed the results and verify the signatures(traceable blind ring signatures) against the transaction payload 293.

Referring again to FIG. 2B, the client node 260 initiates thetransaction 291 by constructing and sending a request to the peer node281, which is an endorser. The client 260 may include an applicationleveraging a supported software development kit (SDK), which utilizes anavailable API to generate a transaction proposal. The proposal is arequest to invoke a chaincode function so that data can be read and/orwritten to the ledger (i.e., write new key value pairs for the assets).The SDK may serve as a shim to package the transaction proposal into aproperly architected format (e.g., protocol buffer over a remoteprocedure call (RPC)) and take the client's cryptographic credentials toproduce a unique signature for the transaction proposal.

In response, the endorsing peer node 281 may verify (a) that thetransaction proposal is well formed, (b) the transaction has not beensubmitted already in the past (replay-attack protection), (c) thesignature is valid, and (d) that the submitter (client 260, in theexample) is properly authorized to perform the proposed operation onthat channel. The endorsing peer node 281 may take the transactionproposal inputs as arguments to the invoked chaincode function. Thechaincode is then executed against a current state database to producetransaction results including a response value, read set, and write set.However, no updates are made to the ledger at this point. In 292, theset of values, along with the endorsing peer node's 281 traceable blindring signature may be passed back as a proposal response 292 to the SDKof the client 260 which parses the payload for the application toconsume.

In response, the application of the client 260 inspects/verifies theendorsing peers signatures and compares the proposal responses todetermine if the proposal response is the same. If the chaincode onlyqueried the ledger, the application would inspect the query response andwould typically not submit the transaction to the ordering node service284. If the client application intends to submit the transaction to theordering node service 284 to update the ledger, the applicationdetermines if the specified endorsement policy has been fulfilled beforesubmitting (i.e., did all peer nodes necessary for the transactionendorse the transaction). Here, the client may include only one ofmultiple parties to the transaction. In this case, each client may havetheir own endorsing node, and each endorsing node will need to endorsethe transaction. The architecture is such that even if an applicationselects not to inspect responses or otherwise forwards an unendorsedtransaction, the endorsement policy will still be enforced by peers andupheld at the commit validation phase.

After successful inspection, in step 293 the client 260 assemblesendorsements into a transaction and broadcasts the transaction proposaland response within a transaction message to the ordering node 284. Thetransaction may contain the read/write sets, the endorsing peerstraceable blind ring signatures and a channel ID. The ordering node 284does not need to inspect the entire content of a transaction in order toperform its operation, instead the ordering node 284 may simply receivetransactions from all channels in the network, order themchronologically by channel, and create blocks of transactions perchannel.

The blocks of the transaction are delivered from the ordering node 284to all peer nodes 281-283 on the channel. The transactions 294 withinthe block are validated to ensure any endorsement policy is fulfilledand to ensure that there have been no changes to ledger state for readset variables since the read set was generated by the transactionexecution. Transactions in the block are tagged as being valid orinvalid. Furthermore, in step 295 each peer node 281-283 appends theblock to the channel's chain, and for each valid transaction the writesets are committed to current state database. An event is emitted, tonotify the client application that the transaction (invocation) has beenimmutably appended to the chain, as well as to notify whether thetransaction was validated or invalidated.

FIG. 3A illustrates an example of a permissioned blockchain network 300,which features a distributed, decentralized peer-to-peer architecture.In this example, a blockchain user 302 may initiate a transaction to thepermissioned blockchain 304. In this example, the transaction can be adeploy, invoke, or query, and may be issued through a client-sideapplication leveraging an SDK, directly through an API, etc. Networksmay provide access to a regulator 306, such as an auditor. A blockchainnetwork operator 308 manages member permissions, such as enrolling theregulator 306 as an “auditor” and the blockchain user 302 as a “client”.An auditor could be restricted only to querying the ledger whereas aclient could be authorized to deploy, invoke, and query certain types ofchaincode.

A blockchain developer 310 can write chaincode and client-sideapplications. The blockchain developer 310 can deploy chaincode directlyto the network through an interface. To include credentials from atraditional data source 312 in chaincode, the developer 310 could use anout-of-band connection to access the data. In this example, theblockchain user 302 connects to the permissioned blockchain 304 througha peer node 314. Before proceeding with any transactions, the peer node314 retrieves the user's enrollment and transaction certificates from acertificate authority 316, which manages user roles and permissions. Insome cases, blockchain users must possess these digital certificates inorder to transact on the permissioned blockchain 304. Meanwhile, a userattempting to utilize chaincode may be required to verify theircredentials on the traditional data source 312. To confirm the user'sauthorization, chaincode can use an out-of-band connection to this datathrough a traditional processing platform 318.

FIG. 3B illustrates another example of a permissioned blockchain network320, which features a distributed, decentralized peer-to-peerarchitecture. In this example, a blockchain user 322 may submit atransaction to the permissioned blockchain 324. In this example, thetransaction can be a deploy, invoke, or query, and may be issued througha client-side application leveraging an SDK, directly through an API,etc. Networks may provide access to a regulator 326, such as an auditor.A blockchain network operator 328 manages member permissions, such asenrolling the regulator 326 as an “auditor” and the blockchain user 322as a “client”. An auditor could be restricted only to querying theledger whereas a client could be authorized to deploy, invoke, and querycertain types of chaincode.

A blockchain developer 330 writes chaincode and client-sideapplications. The blockchain developer 330 can deploy chaincode directlyto the network through an interface. To include credentials from atraditional data source 332 in chaincode, the developer 330 could use anout-of-band connection to access the data. In this example, theblockchain user 322 connects to the network through a peer node 334.Before proceeding with any transactions, the peer node 334 retrieves theuser's enrollment and transaction certificates from the certificateauthority 336. In some cases, blockchain users must possess thesedigital certificates in order to transact on the permissioned blockchain324. Meanwhile, a user attempting to utilize chaincode may be requiredto verify their credentials on the traditional data source 332. Toconfirm the user's authorization, chaincode can use an out-of-bandconnection to this data through a traditional processing platform 338.

FIG. 4 illustrates a system 400 for signing and verifying a traceableblinded ring signature, according to example embodiments. Referring tothe example of FIG. 4, the system 400 includes an endorser node 410(peer node) and a verification node 420. Furthermore, an identity of theendorser node 410 is hidden from the verification node 420. The endorsernode 410 may submit data to a blockchain 430 which is subsequentlyaccessed/retrieved by the verification node 420. As an example, theverification node 420 may be a client system, another peer node in theblockchain, an auditor, and the like, which desire to verify anendorsement performed by the endorser node 410 without learning anidentity of the endorser node 410.

In the example of FIG. 4, the endorser node 410 receives a transactionproposal from a client (not shown) of the blockchain 430 and generatesan endorsement of the transaction proposal based on an invocation ofchaincode with the transaction proposal as input. The endorser node 410may simulate the transaction to validate the transaction. In response tovalidating the transaction, the endorser node 410 may sign thetransaction with a unique key which is associated with the endorser node410. Furthermore, the transaction may be submitted back to the clientwhere it is subsequently forwarded to an orderer, added to a block, andstored in the blockchain 430.

According to various embodiments, the unique key which is used by theendorser node 410 is not a private key, but is instead a blinded privatekey and blinded public key ring, which obscures the identity of theendorser node 410 such that none of the endorser nodes of the blockchain430 can be identified by a participating member of the blockchain 430.The endorser node 410 may perform a first process to get the blindedpublic key ring and blindness factor from the board, and subsequentlysign a response message using the blinded public key ring and his ownblinded private key.

In the example of FIG. 4, the endorser node 410 includes a keygeneration module 412 and a signing module 414. The blind ring signatureis named so because instead of using the original public key ring andprivate key to sign the message, the endorser 410 uses the blindedpublic key ring and his own blinded private key. (The signing processdoes not change). Since the original public key is known by the network,but the blinded public key is not, the original ring signature can belinked to a set of known identities whereas the blind ring signaturecannot be linked to a specific or a set of known identities (hence thename “blind”). To generate the blinded public/private key, the endorsernode 410 adds a blindness factor (a multiplication factor) to theoriginal public/private key. A traceable ring signature allows averifier (e.g., a traceability module 424) to determine whether any twosignatures with regard to the same transaction id have been produced bythe same signer.

The endorsement policy can generally be expressed as {L of (peer_(x) ₁ ,. . . peer_(x) _(N) ) AND/OR H of (peer_(y) ₁ , . . . peer_(y) _(M) )},meaning collecting L unique signatures from the group of (peer_(x) ₁ , .. . peer_(x) _(N) ) and/or collecting H unique signatures from the groupof (peer_(y) ₁ , . . . peer_(y) _(M) ). Thus, the endorsement problemcan be translated to collecting L unique ring signatures from a ring of{pk_(x) ₁ , . . . pk_(x) _(N) } and/or H signatures from a ring of{pk_(y) ₁ , . . . pk_(y) _(M) }. Traceable ring signature can be used toachieve this purpose. It allows you to count how many unique signaturesyou get from a particular ring composition, without revealing who fromthe ring actually signed. In the case of ring signature, the public keyof the ring members are revealed and can be further traced toorganizations. The example embodiments employ a traceable blinded ringsignature method to hide the public keys and blind the identities oforganizations in the endorsement policy. Without loss of generality, weassume a simple endorsement policy as L of {pk₁, . . . , pk_(n)} fordescribing the protocol. More complex case can be easily constructedfrom this simple version. In this example, let G be a multiplicativegroup of prime order q and let g be a generator of G. Let H: {0,1}*→G,H′: {0,1}*→G and H″: {0,1}*→Z_(q) be distinct hash functions (modelledas random oracles). These are the public parameters of the ringsignature.

The endorser node 410 may include the key generation module 412 whichpicks up random element x_(i) in Z_(q) and computes y_(i)=g^(x) ^(i) .The public key of i is pk_(i)={y_(i)} and the corresponding secret keyis {x_(i)}. The endorser peer i registers their public-key with CA. Fora new endorsement policy, the board (authority) may randomly generate adifferent blinding factor r_(i) for each endorser node (ring member i.)The endorsement policy is thus published as: L of pk_(N)={pk′₁, . . . ,pk′_(n)}={pk₁g^(r) ¹ , . . . , pk_(n)g^(r) ^(n) }={g^(x) ¹ g^(r) ¹ , . .. , g^(x) ^(n) g^(r) ^(n) }. Because a blinding factor is added to thepublic key, the identity of organizations is hidden in the endorsementpolicy. The board may secretly communicate each r_(i) to peer iparticipating in the endorsement policy. Assume the message m to beendorsed is the simulated transaction and the issue is the tid(transaction id).

The endorser peer 414 may include a signer module 414 that may use asecret key sk_(i) to endorse/sign a message m∈{0,1}* with respect to tagL=(issue, pk_(N)) as follows:

-   -   1. Compute h=H(L) and σ_(i)=h^(x) ^(i) ^(+r) ^(i) , set        A₀=H′(L,m) and

$A_{1} = ( \frac{\sigma_{i}}{A_{0}} )^{1\text{/}i}$

-   -   2. For all j≠i, compute σ_(j)=A₀A₁ ^(j)∈G. Notice that every        (j,log_(h)(σ_(j))) is on the line defined by (0, log_(h)(A₀))        and (i, x_(i)+r_(i)), where x_(i)+r_(i)=log_(h)(σ_(i))    -   3. Generate signature (c_(N), z_(N)) on (L, m), based on a        zero-knowledge proof of knowledge for the relation derived from        language        {(L,h,σ _(N))|∃i′∈N such that log_(g)(y _(i′))=log_(h)(σ_(i′))}}    -   where σ_(N)=(σ₁, . . . σ_(n)), as follows:        -   (a) Pick up random w_(i)←z_(q) and set a_(i)=g^(w) ^(i) ,            b_(i)=h^(w) ^(i) ∈G        -   (b) Pick up at random z_(j), c_(j)←Z_(q), and set            a_(j)=g^(z) ^(j) y_(i) ^(c) ^(j) , b_(j)=h^(z) ^(j) σ_(j)            ^(c) ^(j) ∈G for j≠i        -   (c) Set c=H″(L,m,A₀,A₁,a_(N),b_(N)) where a_(N)=(a₁, . . . ,            a_(n)) and b_(N)=(b₁, . . . , b_(n)).        -   (d) Set c_(i)=c−Σ_(j≠i)c_(j) (mod q) and            z_(i)=w_(i)−c_(i)(x_(i)+r_(i)) (mod q). Return            (c_(N),z_(N)), where c_(N)=(c₁, . . . c_(n)) and z_(N)=(z₁,            . . . , z_(n)), as a proof of    -   4. Output σ=(A₁,c_(N),z_(N)) as the signature on (L,m)

Verification of endorsements during a transaction, i.e. making sure theyare valid, and unravelling the identities of endorsers for an audit aretwo different operations used for different purposes. Verification ofendorsements during a transaction is done by verifying the traceableblind ring signature against the blinded public key ring and themessage. Hence, the blinded public key ring is sufficient for thisoperation. The purpose of this operation is to ensure the endorsementssatisfy the required endorsement policy and come from legitimateendorsers rather than knowing the real identities of endorsers.

In the example of FIG. 4, the verification node 420 includes averification module 422 and a traceability module 424. To verifysignature σ=(A₁,c_(N),z_(N)) on message m with respect to tag L, theverification module 422 may check the following:

-   -   1. Parse L as (issue,pk_(N)). Check g,A₁ ∈G,c_(i),z_(i)∈Z₁ and        y_(i)∈G for all i∈N. Set h=H(L) and A₀=H′(L,m), and compute        σ_(i)=A₀,A₁ ^(i)∈G for all i∈N.    -   2. Compute a_(i)=g^(z) ^(i) y_(i) ^(c) ^(i) , b_(i)=h^(z) ^(i)        σ_(i) ^(c) ^(i) for all i∈N.    -   3. Check that H″(L,m,A₀,A₁,a_(N),b_(N))≡Σ_(i∈N)c_(i)(mod q),        where a_(N)=(a₁, . . . , a_(n)) and b_(N)=(b₁, . . . , b_(n)).    -   4. If all the above checks are successfully completed, accept,        otherwise reject.

The traceability module 424 may verify that a signature for atransaction has not been used more than once. To check if two signatures(m,σ) and (m′,σ′) with respect to the same tag L are unique, whereσ=(A₁,c_(N),z_(N)) and σ′=(A′₁,c′_(N),z′_(N)), check the following:

-   -   1. Parse L as (issue, pk_(N)). Set h=H(L) and A₀=H′(L, m), and        compute σ_(i)=A₀,A₁ ^(i)∈G for all i∈N. Do the same thing for σ′        and retrieve σ′_(i), for all i∈N.    -   2. For all i∈N, if σ_(i)=σ′_(i), store pk_(i) in TList, where        TList is initially an empty list.    -   3. If Tlist has only one entry or N entries, the two signatures        are not unique and can only be counted as one. Otherwise,        1<#TList<n, the two signatures are independent and can be        counted as two.

If revealing endorsers' identities is required for an audit, thefollowing procedure could be used by an auditor. For example, theauditor receives the blindness factors from all the endorsers and usesthe blindness factors to discover the members in the ring. There couldbe multiple ways for auditors to get the blindness factors, such asoffline communication with endorsers or online through blockchain. Thelatter can be done as follows: when setting up blockchain, all blindnessfactors are encrypted using auditors' public key and stored on theledger. When needed, auditors can read from the ledger the encryptedcontent and decrypt using secret keys to get the plaintext blindnessfactors. To check whether an endorser from the ring has endorsed acertain transaction previously, auditor can ask the endorser to sign thetransaction proposal again. If the new signature is linked to one of theendorsement signatures recorded for this transaction proposal in theledger, this endorser must have endorsed this transaction previously.

FIG. 5 illustrates a method 500 of endorsing a transaction based on atraceable blinded ring signature, according to example embodiments. Forexample, the method 500 may be performed by an endorser node (i.e., anendorsing peer). Referring to FIG. 5, in 510, the method may includereceiving, at the endorser node, a request message from a client systemwhich comprises data to be stored on a blockchain. For example, therequest message may include a blockchain transaction to be executed andstored via the blockchain.

In 520, the method may include determining whether to endorse the datavia invocation of chaincode which receives the data as input andexecutes the data against a current state of the blockchain.Furthermore, in response to a determination to endorse the data, in 530the method may include generating a response message including a resultof the execution and which is signed based on a traceable blinded ringsignature associated with the endorser node. Furthermore, in 540 themethod may include transmitting the generated response message that hasbeen signed with the traceable blinded ring signature to the clientsystem.

According to various embodiments, the traceable blinded ring signaturemay include a traceable ring signature that has been altered with ablinding factor. In some embodiments, the method may further includeblinding an endorser's public/private key via multiplication with arandom multiplication factor. For example, the public/private keys ofthe endorser node may be multiplied with a random multiplication factor.The resulting blinded private key and a blinded public key ring are usedby an endorser to generate the traceable blinded ring signature. Thetraceable blind ring signature is not directly generated by multiplyingthe traceable ring signature with a random multiplication factor. Asdescribed herein, the traceable blinded ring signature hides an identityof a group of endorser nodes including the endorser node which aremembers of the blockchain. In addition, the traceable blinded ringsignature hides an identity of an endorsement policy adhered to by theblockchain. In some embodiments, the generating the response message mayinclude generating the response message to include a list of traceableblinded ring signatures of the plurality of endorser nodes of theblockchain. In some embodiments, the method may further includereceiving a data block from an ordering node of the blockchain, whereinthe data block includes the data that has been further endorsed with arespective traceable blinded ring signature of at least one otherendorser node. In some embodiments, the method may further includestoring the data block within a hash-linked chain of data blocks of theblockchain.

FIG. 6A illustrates an example system 600 that includes a physicalinfrastructure 610 configured to perform various operations according toexample embodiments. Referring to FIG. 6A, the physical infrastructure610 includes a module 612 and a module 614. The module 614 includes ablockchain 620 and a smart contract 630 (which may reside on theblockchain 620), that may execute any of the operational steps 608 (inmodule 612) included in any of the example embodiments. Thesteps/operations 608 may include one or more of the embodimentsdescribed or depicted and may represent output or written informationthat is written or read from one or more smart contracts 630 and/orblockchains 620. The physical infrastructure 610, the module 612, andthe module 614 may include one or more computers, servers, processors,memories, and/or wireless communication devices. Further, the module 612and the module 614 may be a same module.

FIG. 6B illustrates another example system 640 configured to performvarious operations according to example embodiments. Referring to FIG.6B, the system 640 includes a module 612 and a module 614. The module614 includes a blockchain 620 and a smart contract 630 (which may resideon the blockchain 620), that may execute any of the operational steps608 (in module 612) included in any of the example embodiments. Thesteps/operations 608 may include one or more of the embodimentsdescribed or depicted and may represent output or written informationthat is written or read from one or more smart contracts 630 and/orblockchains 620. The physical infrastructure 610, the module 612, andthe module 614 may include one or more computers, servers, processors,memories, and/or wireless communication devices. Further, the module 612and the module 614 may be a same module.

FIG. 6C illustrates an example system configured to utilize a smartcontract configuration among contracting parties and a mediating serverconfigured to enforce the smart contract terms on the blockchainaccording to example embodiments. Referring to FIG. 6C, theconfiguration 650 may represent a communication session, an assettransfer session or a process or procedure that is driven by a smartcontract 630 which explicitly identifies one or more user devices 652and/or 656. The execution, operations and results of the smart contractexecution may be managed by a server 654. Content of the smart contract630 may require digital signatures by one or more of the entities 652and 656 which are parties to the smart contract transaction. The resultsof the smart contract execution may be written to a blockchain 620 as ablockchain transaction. The smart contract 630 resides on the blockchain620 which may reside on one or more computers, servers, processors,memories, and/or wireless communication devices.

FIG. 6D illustrates a system 660 including a blockchain, according toexample embodiments. Referring to the example of FIG. 6D, an applicationprogramming interface (API) gateway 662 provides a common interface foraccessing blockchain logic (e.g., smart contract 630 or other chaincode)and data (e.g., distributed ledger, etc.). In this example, the APIgateway 662 is a common interface for performing transactions (invoke,queries, etc.) on the blockchain by connecting one or more entities 652and 656 to a blockchain peer (i.e., server 654). Here, the server 654 isa blockchain network peer component that holds a copy of the world stateand a distributed ledger allowing clients 652 and 656 to query data onthe world state as well as submit transactions into the blockchainnetwork where, depending on the smart contract 630 and endorsementpolicy, endorsing peers will run the smart contracts 630.

The above embodiments may be implemented in hardware, in a computerprogram executed by a processor, in firmware, or in a combination of theabove. A computer program may be embodied on a computer readable medium,such as a storage medium. For example, a computer program may reside inrandom access memory (“RAM”), flash memory, read-only memory (“ROM”),erasable programmable read-only memory (“EPROM”), electrically erasableprogrammable read-only memory (“EEPROM”), registers, hard disk, aremovable disk, a compact disk read-only memory (“CD-ROM”), or any otherform of storage medium known in the art.

An exemplary storage medium may be coupled to the processor such thatthe processor may read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anapplication specific integrated circuit (“ASIC”). In the alternative,the processor and the storage medium may reside as discrete components.

FIG. 7A illustrates a process 700 of a new block being added to adistributed ledger 720, according to example embodiments, and FIG. 7Billustrates contents of a new data block structure 730 for blockchain,according to example embodiments. Referring to FIG. 7A, clients (notshown) may submit transactions to blockchain nodes 711, 712, and/or 713.Clients may be instructions received from any source to enact activityon the blockchain 720. As an example, clients may be applications thatact on behalf of a requester, such as a device, person or entity topropose transactions for the blockchain. The plurality of blockchainpeers (e.g., blockchain nodes 711, 712, and 713) may maintain a state ofthe blockchain network and a copy of the distributed ledger 720.Different types of blockchain nodes/peers may be present in theblockchain network including endorsing peers which simulate and endorsetransactions proposed by clients and committing peers which verifyendorsements, validate transactions, and commit transactions to thedistributed ledger 720. In this example, the blockchain nodes 711, 712,and 713 may perform the role of endorser node, committer node, or both.

The distributed ledger 720 includes a blockchain which stores immutable,sequenced records in blocks, and a state database 724 (current worldstate) maintaining a current state of the blockchain 722. Onedistributed ledger 720 may exist per channel and each peer maintains itsown copy of the distributed ledger 720 for each channel of which theyare a member. The blockchain 722 is a transaction log, structured ashash-linked blocks where each block contains a sequence of Ntransactions. Blocks may include various components such as shown inFIG. 7B. The linking of the blocks (shown by arrows in FIG. 7A) may begenerated by adding a hash of a prior block's header within a blockheader of a current block. In this way, all transactions on theblockchain 722 are sequenced and cryptographically linked togetherpreventing tampering with blockchain data without breaking the hashlinks. Furthermore, because of the links, the latest block in theblockchain 722 represents every transaction that has come before it. Theblockchain 722 may be stored on a peer file system (local or attachedstorage), which supports an append-only blockchain workload.

The current state of the blockchain 722 and the distributed ledger 722may be stored in the state database 724. Here, the current state datarepresents the latest values for all keys ever included in the chaintransaction log of the blockchain 722. Chaincode invocations executetransactions against the current state in the state database 724. Tomake these chaincode interactions extremely efficient, the latest valuesof all keys are stored in the state database 724. The state database 724may include an indexed view into the transaction log of the blockchain722, it can therefore be regenerated from the chain at any time. Thestate database 724 may automatically get recovered (or generated ifneeded) upon peer startup, before transactions are accepted.

Endorsing nodes receive transactions from clients and endorse thetransaction based on simulated results. Endorsing nodes hold smartcontracts which simulate the transaction proposals. When an endorsingnode endorses a transaction, the endorsing nodes creates a transactionendorsement which is a signed response from the endorsing node to theclient application indicating the endorsement of the simulatedtransaction. The method of endorsing a transaction depends on anendorsement policy which may be specified within chaincode. An exampleof an endorsement policy is “the majority of endorsing peers mustendorse the transaction”. Different channels may have differentendorsement policies. Endorsed transactions are forward by the clientapplication to ordering service 710.

The ordering service 710 accepts endorsed transactions, orders them intoa block, and delivers the blocks to the committing peers. For example,the ordering service 710 may initiate a new block when a threshold oftransactions has been reached, a timer times out, or another condition.In the example of FIG. 7A, blockchain node 712 is a committing peer thathas received a new data new data block 730 for storage on blockchain720. The first block in the blockchain may be referred to as a genesisblock which includes information about the blockchain, its members, thedata stored therein, etc.

The ordering service 710 may be made up of a cluster of orderers. Theordering service 710 does not process transactions, smart contracts, ormaintain the shared ledger. Rather, the ordering service 710 may acceptthe endorsed transactions and specifies the order in which thosetransactions are committed to the distributed ledger 720. Thearchitecture of the blockchain network may be designed such that thespecific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.)becomes a pluggable component.

Transactions are written to the distributed ledger 720 in a consistentorder. The order of transactions is established to ensure that theupdates to the state database 724 are valid when they are committed tothe network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin,etc.) where ordering occurs through the solving of a cryptographicpuzzle, or mining, in this example the parties of the distributed ledger720 may choose the ordering mechanism that best suits that network.

When the ordering service 710 initializes a new data block 730, the newdata block 730 may be broadcast to committing peers (e.g., blockchainnodes 711, 712, and 713). In response, each committing peer validatesthe transaction within the new data block 730 by checking to make surethat the read set and the write set still match the current world statein the state database 724. Specifically, the committing peer candetermine whether the read data that existed when the endorserssimulated the transaction is identical to the current world state in thestate database 724. When the committing peer validates the transaction,the transaction is written to the blockchain 722 on the distributedledger 720, and the state database 724 is updated with the write datafrom the read-write set. If a transaction fails, that is, if thecommitting peer finds that the read-write set does not match the currentworld state in the state database 724, the transaction ordered into ablock will still be included in that block, but it will be marked asinvalid, and the state database 724 will not be updated.

Referring to FIG. 7B, a new data block 730 (also referred to as a datablock) that is stored on the blockchain 722 of the distributed ledger720 may include multiple data segments such as a block header 740, blockdata 750, and block metadata 760. It should be appreciated that thevarious depicted blocks and their contents, such as new data block 730and its contents. shown in FIG. 7B are merely examples and are not meantto limit the scope of the example embodiments. The new data block 730may store transactional information of N transaction(s) (e.g., 1, 10,100, 500, 1000, 2000, 3000, etc.) within the block data 750. The newdata block 730 may also include a link to a previous block (e.g., on theblockchain 722 in FIG. 7A) within the block header 740. In particular,the block header 740 may include a hash of a previous block's header.The block header 740 may also include a unique block number, a hash ofthe block data 750 of the new data block 730, and the like. The blocknumber of the new data block 730 may be unique and assigned in variousorders, such as an incremental/sequential order starting from zero.

The block data 750 may store transactional information of eachtransaction that is recorded within the new data block 730. For example,the transaction data may include one or more of a type of thetransaction, a version, a timestamp, a channel ID of the distributedledger 720, a transaction ID, an epoch, a payload visibility, achaincode path (deploy tx), a chaincode name, a chaincode version, input(chaincode and functions), a client (creator) identify such as a publickey and certificate, a signature of the client, identities of endorsers,endorser signatures, a proposal hash, chaincode events, response status,namespace, a read set (list of key and version read by the transaction,etc.), a write set (list of key and value, etc.), a start key, an endkey, a list of keys, a Merkel tree query summary, and the like. Thetransaction data may be stored for each of the N transactions.

In some embodiments, the block data 750 may also store traceable blindring signature (TBRS) data 752 which adds the traceable blind ringsignatures to the hash-linked chain of blocks in the blockchain 722.Traditional endorsement data is composed of a list of endorser'sidentity (certificate, public key) and endorser's signature. In theexample embodiments, modified endorsement data is composed of a blindedpublic key ring (containing different blinded public keys) and a list oftraceable blind ring signatures corresponding to the public keys.Accordingly, the TBRS data 752 can be stored in an immutable log ofblocks on the distributed ledger 720. However, the TBRS data 752 cannotbe used to identify any of the endorsers or an endorsement policy thatis adhered to by the blockchain 722. The benefit of such a system isthat endorsements can be performed and verified while still preservingthe privacy of the endorsing peers. Although in FIG. 7B the new data 752is depicted in the block data 750 but could also be located in the blockheader 740 or the block metadata 760.

The block metadata 760 may store multiple fields of metadata (e.g., as abyte array, etc.). Metadata fields may include signature on blockcreation, a reference to a last configuration block, a transactionfilter identifying valid and invalid transactions within the block, lastoffset persisted of an ordering service that ordered the block, and thelike. The signature, the last configuration block, and the orderermetadata may be added by the ordering service 710. Meanwhile, acommitter of the block (such as blockchain node 712) may addvalidity/invalidity information based on an endorsement policy,verification of read/write sets, and the like. The transaction filtermay include a byte array of a size equal to the number of transactionsin the block data 750 and a validation code identifying whether atransaction was valid/invalid.

FIG. 7C illustrates an embodiment of a blockchain 770 for digitalcontent in accordance with the embodiments described herein. The digitalcontent may include one or more files and associated information. Thefiles may include media, images, video, audio, text, links, graphics,animations, web pages, documents, or other forms of digital content. Theimmutable, append-only aspects of the blockchain serve as a safeguard toprotect the integrity, validity, and authenticity of the digitalcontent, making it suitable use in legal proceedings where admissibilityrules apply or other settings where evidence is taken in toconsideration or where the presentation and use of digital informationis otherwise of interest. In this case, the digital content may bereferred to as digital evidence.

The blockchain may be formed in various ways. In one embodiment, thedigital content may be included in and accessed from the blockchainitself. For example, each block of the blockchain may store a hash valueof reference information (e.g., header, value, etc.) along theassociated digital content. The hash value and associated digitalcontent may then be encrypted together. Thus, the digital content ofeach block may be accessed by decrypting each block in the blockchain,and the hash value of each block may be used as a basis to reference aprevious block. This may be illustrated as follows:

Block 1 Block 2 . . . Block N Hash Value 1 Hash Value 2 Hash Value NDigital Content 1 Digital Content 2 Digital Content N

In one embodiment, the digital content may be not included in theblockchain. For example, the blockchain may store the encrypted hashesof the content of each block without any of the digital content. Thedigital content may be stored in another storage area or memory addressin association with the hash value of the original file. The otherstorage area may be the same storage device used to store the blockchainor may be a different storage area or even a separate relationaldatabase. The digital content of each block may be referenced oraccessed by obtaining or querying the hash value of a block of interestand then looking up that has value in the storage area, which is storedin correspondence with the actual digital content. This operation may beperformed, for example, a database gatekeeper. This may be illustratedas follows:

Blockchain Storage Area Block 1 Hash Value Block 1 Hash Value . . .Content . . . . . . Block N Hash Value Block N Hash Value . . . Content

In the example embodiment of FIG. 7C, the blockchain 770 includes anumber of blocks 778 ₁, 778 ₂, . . . 778 _(N) cryptographically linkedin an ordered sequence, where N≥1. The encryption used to link theblocks 778 ₁, 778 ₂, . . . 778 _(N) may be any of a number of keyed orun-keyed Hash functions. In one embodiment, the blocks 778 ₁, 778 ₂, . .. 778 _(N) are subject to a hash function which produces n-bitalphanumeric outputs (where n is 256 or another number) from inputs thatare based on information in the blocks. Examples of such a hash functioninclude, but are not limited to, a SHA-type (SHA stands for Secured HashAlgorithm) algorithm, Merkle-Damgard algorithm, HAIFA algorithm,Merkle-tree algorithm, nonce-based algorithm, and anon-collision-resistant PRF algorithm. In another embodiment, the blocks778 ₁, 778 ₂, . . . , 778 _(N) may be cryptographically linked by afunction that is different from a hash function. For purposes ofillustration, the following description is made with reference to a hashfunction, e.g., SHA-2.

Each of the blocks 778 ₁, 778 ₂, . . . , 778 _(N) in the blockchainincludes a header, a version of the file, and a value. The header andthe value are different for each block as a result of hashing in theblockchain. In one embodiment, the value may be included in the header.As described in greater detail below, the version of the file may be theoriginal file or a different version of the original file.

The first block 778 ₁ in the blockchain is referred to as the genesisblock and includes the header 772 ₁, original file 774 ₁, and an initialvalue 776 ₁. The hashing scheme used for the genesis block, and indeedin all subsequent blocks, may vary. For example, all the information inthe first block 778 ₁ may be hashed together and at one time, or each ora portion of the information in the first block 778 ₁ may be separatelyhashed and then a hash of the separately hashed portions may beperformed.

The header 772 ₁ may include one or more initial parameters, which, forexample, may include a version number, timestamp, nonce, rootinformation, difficulty level, consensus protocol, duration, mediaformat, source, descriptive keywords, and/or other informationassociated with original file 774 ₁ and/or the blockchain. The header772 ₁ may be generated automatically (e.g., by blockchain networkmanaging software) or manually by a blockchain participant. Unlike theheader in other blocks 778 ₂ to 778 _(N) in the blockchain, the header772 ₁ in the genesis block does not reference a previous block, simplybecause there is no previous block.

The original file 774 ₁ in the genesis block may be, for example, dataas captured by a device with or without processing prior to itsinclusion in the blockchain. The original file 774 ₁ is received throughthe interface of the system from the device, media source, or node. Theoriginal file 774 ₁ is associated with metadata, which, for example, maybe generated by a user, the device, and/or the system processor, eithermanually or automatically. The metadata may be included in the firstblock 778 ₁ in association with the original file 774 ₁.

The value 776 ₁ in the genesis block is an initial value generated basedon one or more unique attributes of the original file 774 ₁. In oneembodiment, the one or more unique attributes may include the hash valuefor the original file 774 ₁, metadata for the original file 774 ₁, andother information associated with the file. In one implementation, theinitial value 776 ₁ may be based on the following unique attributes:

-   -   1) SHA-2 computed hash value for the original file    -   2) originating device ID    -   3) starting timestamp for the original file    -   4) initial storage location of the original file    -   5) blockchain network member ID for software to currently        control the original file and associated metadata

The other blocks 778 ₂ to 778 _(N) in the blockchain also have headers,files, and values. However, unlike the first block 772 ₁, each of theheaders 772 ₂ to 772 _(N) in the other blocks includes the hash value ofan immediately preceding block. The hash value of the immediatelypreceding block may be just the hash of the header of the previous blockor may be the hash value of the entire previous block. By including thehash value of a preceding block in each of the remaining blocks, a tracecan be performed from the Nth block back to the genesis block (and theassociated original file) on a block-by-block basis, as indicated byarrows 780, to establish an auditable and immutable chain-of-custody.

Each of the header 772 ₂ to 772 _(N) in the other blocks may alsoinclude other information, e.g., version number, timestamp, nonce, rootinformation, difficulty level, consensus protocol, and/or otherparameters or information associated with the corresponding files and/orthe blockchain in general.

The files 774 ₂ to 774 _(N) in the other blocks may be equal to theoriginal file or may be a modified version of the original file in thegenesis block depending, for example, on the type of processingperformed. The type of processing performed may vary from block toblock. The processing may involve, for example, any modification of afile in a preceding block, such as redacting information or otherwisechanging the content of, taking information away from, or adding orappending information to the files.

Additionally, or alternatively, the processing may involve merelycopying the file from a preceding block, changing a storage location ofthe file, analyzing the file from one or more preceding blocks, movingthe file from one storage or memory location to another, or performingaction relative to the file of the blockchain and/or its associatedmetadata. Processing which involves analyzing a file may include, forexample, appending, including, or otherwise associating variousanalytics, statistics, or other information associated with the file.

The values in each of the other blocks 776 ₂ to 776 _(N) in the otherblocks are unique values and are all different as a result of theprocessing performed. For example, the value in any one blockcorresponds to an updated version of the value in the previous block.The update is reflected in the hash of the block to which the value isassigned. The values of the blocks therefore provide an indication ofwhat processing was performed in the blocks and also permit a tracingthrough the blockchain back to the original file. This tracking confirmsthe chain-of-custody of the file throughout the entire blockchain.

For example, consider the case where portions of the file in a previousblock are redacted, blocked out, or pixelated in order to protect theidentity of a person shown in the file. In this case, the blockincluding the redacted file will include metadata associated with theredacted file, e.g., how the redaction was performed, who performed theredaction, timestamps where the redaction(s) occurred, etc. The metadatamay be hashed to form the value. Because the metadata for the block isdifferent from the information that was hashed to form the value in theprevious block, the values are different from one another and may berecovered when decrypted.

In one embodiment, the value of a previous block may be updated (e.g., anew hash value computed) to form the value of a current block when anyone or more of the following occurs. The new hash value may be computedby hashing all or a portion of the information noted below, in thisexample embodiment.

-   -   a) new SHA-2 computed hash value if the file has been processed        in any way (e.g., if the file was redacted, copied, altered,        accessed, or some other action was taken)    -   b) new storage location for the file    -   c) new metadata identified associated with the file    -   d) transfer of access or control of the file from one blockchain        participant to another blockchain participant

FIG. 7D illustrates an embodiment of a block which may represent thestructure of the blocks in the blockchain 790 in accordance with oneembodiment. The block, Block_(i), includes a header 772 _(i), a file 774_(i), and a value 776 _(i).

The header 772 _(i) includes a hash value of a previous blockBlock_(i-1) and additional reference information, which, for example,may be any of the types of information (e.g., header informationincluding references, characteristics, parameters, etc.) discussedherein. All blocks reference the hash of a previous block except, ofcourse, the genesis block. The hash value of the previous block may bejust a hash of the header in the previous block or a hash of all or aportion of the information in the previous block, including the file andmetadata.

The file 774 _(i) includes a plurality of data, such as Data 1, Data 2,. . . , Data N in sequence. The data are tagged with metadata Metadata1, Metadata 2, . . . , Metadata N which describe the content and/orcharacteristics associated with the data. For example, the metadata foreach data may include information to indicate a timestamp for the data,process the data, keywords indicating the persons or other contentdepicted in the data, and/or other features that may be helpful toestablish the validity and content of the file as a whole, andparticularly its use a digital evidence, for example, as described inconnection with an embodiment discussed below. In addition to themetadata, each data may be tagged with reference REF₁, REF₂, . . . ,REF_(N) to a previous data to prevent tampering, gaps in the file, andsequential reference through the file.

Once the metadata is assigned to the data (e.g., through a smartcontract), the metadata cannot be altered without the hash changing,which can easily be identified for invalidation. The metadata, thus,creates a data log of information that may be accessed for use byparticipants in the blockchain.

The value 776 _(i) is a hash value or other value computed based on anyof the types of information previously discussed. For example, for anygiven block Block_(i), the value for that block may be updated toreflect the processing that was performed for that block, e.g., new hashvalue, new storage location, new metadata for the associated file,transfer of control or access, identifier, or other action orinformation to be added. Although the value in each block is shown to beseparate from the metadata for the data of the file and header, thevalue may be based, in part or whole, on this metadata in anotherembodiment.

Once the blockchain 770 is formed, at any point in time, the immutablechain-of-custody for the file may be obtained by querying the blockchainfor the transaction history of the values across the blocks. This query,or tracking procedure, may begin with decrypting the value of the blockthat is most currently included (e.g., the last (N^(th)) block), andthen continuing to decrypt the value of the other blocks until thegenesis block is reached and the original file is recovered. Thedecryption may involve decrypting the headers and files and associatedmetadata at each block, as well.

Decryption is performed based on the type of encryption that took placein each block. This may involve the use of private keys, public keys, ora public key-private key pair. For example, when asymmetric encryptionis used, blockchain participants or a processor in the network maygenerate a public key and private key pair using a predeterminedalgorithm. The public key and private key are associated with each otherthrough some mathematical relationship. The public key may bedistributed publicly to serve as an address to receive messages fromother users, e.g., an IP address or home address. The private key iskept secret and used to digitally sign messages sent to other blockchainparticipants. The signature is included in the message so that therecipient can verify using the public key of the sender. This way, therecipient can be sure that only the sender could have sent this message.

Generating a key pair may be analogous to creating an account on theblockchain, but without having to actually register anywhere. Also,every transaction that is executed on the blockchain is digitally signedby the sender using their private key. This signature ensures that onlythe owner of the account can track and process (if within the scope ofpermission determined by a smart contract) the file of the blockchain.

FIG. 8 illustrates an example system 800 that supports one or more ofthe example embodiments described and/or depicted herein. The system 800comprises a computer system/server 802, which is operational withnumerous other general purpose or special purpose computing systemenvironments or configurations. Examples of well-known computingsystems, environments, and/or configurations that may be suitable foruse with computer system/server 802 include, but are not limited to,personal computer systems, server computer systems, thin clients, thickclients, hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputer systems, mainframe computersystems, and distributed cloud computing environments that include anyof the above systems or devices, and the like.

Computer system/server 802 may be described in the general context ofcomputer system-executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 802 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 8, computer system/server 802 in cloud computing node800 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 802 may include, but are notlimited to, one or more processors or processing units 804, a systemmemory 806, and a bus that couples various system components includingsystem memory 806 to processor 804.

The bus represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnects (PCI) bus.

Computer system/server 802 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 802, and it includes both volatileand non-volatile media, removable and non-removable media. System memory806, in one embodiment, implements the flow diagrams of the otherfigures. The system memory 806 can include computer system readablemedia in the form of volatile memory, such as random-access memory (RAM)810 and/or cache memory 812. Computer system/server 802 may furtherinclude other removable/non-removable, volatile/non-volatile computersystem storage media. By way of example only, storage system 814 can beprovided for reading from and writing to a non-removable, non-volatilemagnetic media (not shown and typically called a “hard drive”). Althoughnot shown, a magnetic disk drive for reading from and writing to aremovable, non-volatile magnetic disk (e.g., a “floppy disk”), and anoptical disk drive for reading from or writing to a removable,non-volatile optical disk such as a CD-ROM, DVD-ROM or other opticalmedia can be provided. In such instances, each can be connected to thebus by one or more data media interfaces. As will be further depictedand described below, memory 806 may include at least one program producthaving a set (e.g., at least one) of program modules that are configuredto carry out the functions of various embodiments of the application.

Program/utility 816, having a set (at least one) of program modules 818,may be stored in memory 806 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 818 generally carry out the functionsand/or methodologies of various embodiments of the application asdescribed herein.

As will be appreciated by one skilled in the art, aspects of the presentapplication may be embodied as a system, method, or computer programproduct. Accordingly, aspects of the present application may take theform of an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present application may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Computer system/server 802 may also communicate with one or moreexternal devices 820 such as a keyboard, a pointing device, a display822, etc.; one or more devices that enable a user to interact withcomputer system/server 802; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 802 to communicate withone or more other computing devices. Such communication can occur viaI/O interfaces 824. Still yet, computer system/server 802 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 826. As depicted, network adapter 826communicates with the other components of computer system/server 802 viaa bus. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 802. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Although an exemplary embodiment of at least one of a system, method,and non-transitory computer readable medium has been illustrated in theaccompanied drawings and described in the foregoing detaileddescription, it will be understood that the application is not limitedto the embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions as set forth and defined by thefollowing claims. For example, the capabilities of the system of thevarious figures can be performed by one or more of the modules orcomponents described herein or in a distributed architecture and mayinclude a transmitter, receiver or pair of both. For example, all orpart of the functionality performed by the individual modules, may beperformed by one or more of these modules. Further, the functionalitydescribed herein may be performed at various times and in relation tovarious events, internal or external to the modules or components. Also,the information sent between various modules can be sent between themodules via at least one of: a data network, the Internet, a voicenetwork, an Internet Protocol network, a wireless device, a wired deviceand/or via plurality of protocols. Also, the messages sent or receivedby any of the modules may be sent or received directly and/or via one ormore of the other modules.

One skilled in the art will appreciate that a “system” could be embodiedas a personal computer, a server, a console, a personal digitalassistant (PDA), a cell phone, a tablet computing device, a smartphoneor any other suitable computing device, or combination of devices.Presenting the above-described functions as being performed by a“system” is not intended to limit the scope of the present applicationin any way but is intended to provide one example of many embodiments.Indeed, methods, systems and apparatuses disclosed herein may beimplemented in localized and distributed forms consistent with computingtechnology.

It should be noted that some of the system features described in thisspecification have been presented as modules, in order to moreparticularly emphasize their implementation independence. For example, amodule may be implemented as a hardware circuit comprising custom verylarge-scale integration (VLSI) circuits or gate arrays, off-the-shelfsemiconductors such as logic chips, transistors, or other discretecomponents. A module may also be implemented in programmable hardwaredevices such as field programmable gate arrays, programmable arraylogic, programmable logic devices, graphics processing units, or thelike.

A module may also be at least partially implemented in software forexecution by various types of processors. An identified unit ofexecutable code may, for instance, comprise one or more physical orlogical blocks of computer instructions that may, for instance, beorganized as an object, procedure, or function. Nevertheless, theexecutables of an identified module need not be physically locatedtogether but may comprise disparate instructions stored in differentlocations which, when joined logically together, comprise the module andachieve the stated purpose for the module. Further, modules may bestored on a computer-readable medium, which may be, for instance, a harddisk drive, flash device, random access memory (RAM), tape, or any othersuch medium used to store data.

Indeed, a module of executable code could be a single instruction, ormany instructions, and may even be distributed over several differentcode segments, among different programs, and across several memorydevices. Similarly, operational data may be identified and illustratedherein within modules and may be embodied in any suitable form andorganized within any suitable type of data structure. The operationaldata may be collected as a single data set or may be distributed overdifferent locations including over different storage devices, and mayexist, at least partially, merely as electronic signals on a system ornetwork.

It will be readily understood that the components of the application, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations.Thus, the detailed description of the embodiments is not intended tolimit the scope of the application as claimed but is merelyrepresentative of selected embodiments of the application.

One having ordinary skill in the art will readily understand that theabove may be practiced with steps in a different order, and/or withhardware elements in configurations that are different than those whichare disclosed. Therefore, although the application has been describedbased upon these preferred embodiments, it would be apparent to those ofskill in the art that certain modifications, variations, and alternativeconstructions would be apparent.

While preferred embodiments of the present application have beendescribed, it is to be understood that the embodiments described areillustrative only and the scope of the application is to be definedsolely by the appended claims when considered with a full range ofequivalents and modifications (e.g., protocols, hardware devices,software platforms etc.) thereto.

What is claimed is:
 1. An endorser node, comprising: a network interfaceconfigured to receive a request message from a client system whichcomprises data to be stored on a blockchain; and a processor configuredto determine to endorse the data via invocation of chaincode whichreceives the data as input and executes the data against a current stateof the blockchain, and generate a response message that includes aresult of the execution and sign the response message with a traceableblinded ring signature that comprises a blinded public key setcontaining blinded public keys of a plurality of endorser nodes of theblockchain and a blinded private key of the endorser node, wherein thenetwork interface is further configured to transmit the signed responsemessage to the client system.
 2. The endorser node of claim 1, whereinthe traceable blinded ring signature comprises a private key signatureof the endorser node that has been altered with the blinding factor. 3.The endorser node of claim 1, wherein the processor is furtherconfigured to blind the private key of the endorser node and generatethe traceable blind ring signature based on the blinded private key andthe blinded public keys of the plurality of endorser nodes.
 4. Theendorser node of claim 1, wherein the traceable blinded ring signaturehides identities of the plurality of endorser nodes to other users ofthe blockchain.
 5. The endorser node of claim 1, wherein the blindingfactor of the traceable blinded ring signature prevents traceabilityback to the plurality of endorser nodes of the blockchain.
 6. Theendorser node of claim 1, wherein the network interface is furtherconfigured to receive a data block from an ordering node of theblockchain, wherein the data block includes the data that has beenfurther endorsed with a respective traceable blinded ring signature ofat least one other endorser node.
 7. The endorser node of claim 6,wherein the processor is further configured to store the data blockwithin a hash-linked chain of data blocks of the blockchain.
 8. A methodcomprising: receiving, at an endorser node, a request message from aclient system which comprises data to be stored on a blockchain;determining to endorse the data via invocation of chaincode whichreceives the data as input and executes the data against a current stateof the blockchain; generating a response message including a result ofthe execution and signing the response message with a traceable blindedring signature that comprises a blinded public key set containingblinded public keys of a plurality of endorser nodes of the blockchainand a blinded private key of the endorser node; and transmitting thesigned response message to the client system.
 9. The method of claim 8,wherein the traceable blinded ring signature comprises a private keysignature of the endorser node that has been altered with the blindingfactor.
 10. The method of claim 8, wherein the method further comprisesblinding the private key of the endorser node and generating thetraceable blind ring signature based on the blinded private key and theblinded public keys of the plurality of endorser nodes.
 11. The methodof claim 8, wherein the traceable blinded ring signature hides anidentity of the plurality of endorser nodes to other users of theblockchain.
 12. The method of claim 8, wherein the blinding factor ofthe traceable blinded ring signature prevents traceability back to theplurality of endorser nodes of the blockchain.
 13. The method of claim8, further comprising receiving a data block from an ordering node ofthe blockchain, wherein the data block includes the data that has beenfurther endorsed with a respective traceable blinded ring signature ofat least one other endorser node.
 14. The method of claim 13, furthercomprising storing the data block within a hash-linked chain of datablocks of the blockchain.
 15. A non-transitory computer readable mediumcomprising instructions that when read by a processor cause theprocessor to perform a method comprising: receiving, at an endorsernode, a request message from a client system which comprises data to bestored on a blockchain; determining to endorse the data via invocationof chaincode which receives the data as input and executes the dataagainst a current state of the blockchain; generating a response messageincluding a result of the execution and signing the response messagewith a traceable blinded ring signature that comprises a blinded publickey set containing blinded public keys of a plurality of endorser nodesof the blockchain and a blinded private key of the endorser node; andtransmitting the signed response message to the client system.
 16. Thenon-transitory computer readable medium of claim 15, wherein thetraceable blinded ring signature comprises a private key signature ofthe endorser node that has been altered with the blinding factor. 17.The non-transitory computer readable medium of claim 15, wherein themethod further comprises blinding the private key of the endorser nodeand generating the traceable blind ring signature based on the blindedpublic keys of the plurality of endorser nodes.
 18. The non-transitorycomputer readable medium of claim 15, wherein the traceable blinded ringsignature hides an identity of the plurality of endorser nodes to otherusers of the blockchain.